One of such functionalities is related to the capability of what is called the connection-health-checking. Connection health checking checks the DB physical connection before a logical connections is given to the application. If some of the checks gives a wrong result, the connection itself is marked as "unusable", a brand new physical connection is created into the pool, and the connection request operation is repeated once again.
All this process is transparent for the application, which is still waiting for a connection. This applies to connections that are requested from the pool. Oracle with "Maximum open cursors exceeded", etc. Just explicitly close all opened resources, no excuses. I would rather not use drivers that do no conform to the specs then — Enerccio.
As BalusC points out, it is good defensive programming to explicitly close the connection instead of hardwiring a dependency on a particular provider. Brian Agnew Brian Agnew k 36 36 gold badges silver badges bronze badges.
When I insert a "finally" eclipse likes to highlight it telling me it's wrong. I moved the "close" statements to the finally, but they're just saying "sqlexception", any suggestions? You have to handle that. See DbUtils. Show 2 more comments.
You should do this with any object that implements AutoClosable. Joe Joe 4 4 silver badges 11 11 bronze badges. So you do not have to manually close connection in this case? You do not have to explicitly close the connection. It will be closed when the end of the try code block is reached. What is the Java version requirement for this to work?
Alex Miller Alex Miller This ties down various finite resources on the client and server side. If a client does this kind of thing too much, it can cause problems for the client itself, the database service, and possibly even for other applications running on client or server machine. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.
Post as a guest Name. Email Required, but never shown. You load the JDBC driver like this:. Each JDBC driver has a primary driver class that initializes the driver when it is loaded. For instance, to load the H2Database driver, you write this:. You only have to load the driver once. You do not need to load it before every connection opened. Only before the first JDBC connection opened. DriverManager class method getConnection. There are three variants of this method. I will show each variant in the following sections.
The first method variant only takes a URL to the database as parameter. This is how calling getConnection only with the URL as parameter looks:. The url is the url to your database. SQL statements are executed and results are returned within the context of a connection. A Connection object's database is able to provide information describing its tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, and so on.
This information is obtained with the getMetaData method. By default a Connection object is in auto-commit mode, which means that it automatically commits changes after executing each statement. If auto-commit mode has been disabled, the method commit must be called explicitly in order to commit changes; otherwise, database changes will not be saved.
A user may enter a custom mapping for a UDT in this type map. If so, the getObject method will map the UDT to the class indicated. If there is no entry, the UDT will be mapped using the standard mapping.
A user may create a new type map, which is a java. Map object, make an entry in it, and pass it to the java. In this case, the method will use the given type map instead of the one associated with the connection.
The code fragment retrieves the type map for the Connection object con , inserts the entry into it, and then sets the type map with the new entry as the connection's type map. String, java. Blob createBlob Constructs an object that implements the Blob interface. Clob createClob Constructs an object that implements the Clob interface. Statement createStatement int resultSetType, int resultSetConcurrency Creates a Statement object that will generate ResultSet objects with the given type and concurrency.
Statement createStatement int resultSetType, int resultSetConcurrency, int resultSetHoldability Creates a Statement object that will generate ResultSet objects with the given type, concurrency, and holdability. String getCatalog Retrieves this Connection object's current catalog name. Properties getClientInfo Returns a list containing the name and current value of each client info property supported by the driver. String getClientInfo String name Returns the value of the client info property specified by name.
String getSchema Retrieves this Connection object's current schema name. PreparedStatement prepareStatement String sql, int autoGeneratedKeys Creates a default PreparedStatement object that has the capability to retrieve auto-generated keys.
PreparedStatement prepareStatement String sql, int[] columnIndexes Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array. PreparedStatement prepareStatement String sql, String [] columnNames Creates a default PreparedStatement object capable of returning the auto-generated keys designated by the given array.
Savepoint setSavepoint Creates an unnamed savepoint in the current transaction and returns the new Savepoint object that represents it. Savepoint setSavepoint String name Creates a savepoint with the given name in the current transaction and returns the new Savepoint object that represents it. Methods inherited from interface java. This level allows a row changed by one transaction to be read by another transaction before any changes in that row have been committed a "dirty read".
If any of the changes are rolled back, the second transaction will have retrieved an invalid row. This level only prohibits a transaction from reading a row with uncommitted changes in it. This level prohibits a transaction from reading a row with uncommitted changes in it, and it also prohibits the situation where one transaction reads a row, a second transaction alters the row, and the first transaction rereads the row, getting different values the second time a "non-repeatable read".
SQL statements without parameters are normally executed using Statement objects. If the same SQL statement is executed many times, it may be more efficient to use a PreparedStatement object. The holdability of the created result sets can be determined by calling getHoldability. This object can then be used to efficiently execute this statement multiple times. Note: This method is optimized for handling parametric SQL statements that benefit from precompilation.
If the driver supports precompilation, the method prepareStatement will send the statement to the database for precompilation. Some drivers may not support precompilation. In this case, the statement may not be sent to the database until the PreparedStatement object is executed.
This has no direct effect on users; however, it does affect which methods throw certain SQLException objects. Parameters: sql - an SQL statement that may contain one or more '? The CallableStatement object provides methods for setting up its IN and OUT parameters, and methods for executing the call to a stored procedure. Note: This method is optimized for handling stored procedure call statements. Some drivers may send the call statement to the database when the method prepareCall is done; others may wait until the CallableStatement object is executed.
This has no direct effect on users; however, it does affect which method throws certain SQLExceptions. Typically this statement is specified using JDBC call escape syntax. This method returns the native form of the statement that the driver would have sent. If a connection is in auto-commit mode, then all its SQL statements will be executed and committed as individual transactions.
Otherwise, its SQL statements are grouped into transactions that are terminated by a call to either the method commit or the method rollback. By default, new connections are in auto-commit mode. The commit occurs when the statement completes. For Select statements, the statement is complete when the associated result set is closed. For CallableStatement objects or for statements that return multiple results, the statement is complete when all of the associated result sets have been closed, and all update counts and output parameters have been retrieved.
NOTE: If this method is called during a transaction and the auto-commit mode is changed, the transaction is committed. If setAutoCommit is called and the auto-commit mode is not changed, the call is a no-op. Parameters: autoCommit - true to enable auto-commit mode; false to disable it Throws: SQLException - if a database access error occurs, setAutoCommit true is called while participating in a distributed transaction, or this method is called on a closed connection See Also: getAutoCommit getAutoCommit boolean getAutoCommit throws SQLException Retrieves the current auto-commit mode for this Connection object.
This method should be used only when auto-commit mode has been disabled. Throws: SQLException - if a database access error occurs, this method is called while participating in a distributed transaction, if this method is called on a closed conection or this Connection object is in auto-commit mode See Also: setAutoCommit boolean rollback void rollback throws SQLException Undoes all changes made in the current transaction and releases any database locks currently held by this Connection object.
Throws: SQLException - if a database access error occurs, this method is called while participating in a distributed transaction, this method is called on a closed connection or this Connection object is in auto-commit mode See Also: setAutoCommit boolean close void close throws SQLException Releases this Connection object's database and JDBC resources immediately instead of waiting for them to be automatically released.
Calling the method close on a Connection object that is already closed is a no-op. It is strongly recommended that an application explicitly commits or rolls back an active transaction prior to calling the close method.
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